1. Field of the Invention
The present invention relates to a terminal pad of a flexure for a head suspension connected to a functional part such as slider and a method of forming the terminal pad.
2. Description of the Related Art
A hard disk drive (HDD) has a hard disk and a head suspension for supporting a magnetic head (functional part). The magnetic head is connected to the wiring of the head suspension to read and write data from and to the hard disk.
Recently, it is required for a HDD the higher recording density and higher reliability. For this, additional functions may be incorporated into a magnetic head based on components such as a heater for controlling a flying height and a head disk interface (HDI) sensor other than the usual read/write elements. Further additional functions such as energy assisted recording are considered to be incorporated into the magnetic head. Accordingly, there are a lot of magnetic heads with ten or more terminals including the terminals for the functions as well as the ground terminal.
In the current HDD, a minute slider so-called “Femto slider” having the width of mere 0.7 mm is used for a magnetic head. To connect the magnetic head to wiring of a head suspension, the ten or more terminals arranged within the width of 0.7 mm of the slider have to be joined to the respective terminals of the wiring of the head suspension without short circuit.
Such a connection between terminals of a slider and a head suspension is often carried out by reflow soldering with the use of micro solder balls as disclosed in U.S. Pat. No. 7,239,484B2, U.S. Pat. No. 7,984,545B2, U.S. Pat. No. 8,213,121B2, U.S. Pat. No. 8,295,011B2, and U.S. Pat. No. 8,295,012B1. In particular, the terminals of the slider are placed close to and orthogonal to the terminals of the head suspension. Then, the micro solder ball is put in each one depression between the orthogonal terminals and is reflowed to join the orthogonal terminals together (FIGS. 4(a) and 4(b) of U.S. Pat. No. 7,984,545B2, for instance).
The terminals of the slider are formed on the side surface of the slider at positions slightly displaced inside (toward the upper side) relative to the lower surface of the slider. Accordingly, the terminals of the slider keep a slight distance from the terminals of the head suspension. The distance has an insignificant effect on the connection between the terminals of the slider and the head suspension if the terminals are relatively large. This is because the solder ball is relatively large and is reflowed to form a clear fillet shape spanning between the terminals.
Currently, the terminals are arranged in high density as mentioned above to become relatively small, and the solder ball also becomes relatively small by necessity.
Accordingly, the solder does not form the clear fillet spanning between the terminals of the head suspension and the slider and having the sufficient thickness. This increases risk for connection failure and is desired to be promptly solved.
Such a connection between terminals using a solder ball is also applicable at a tail portion of a flexure of the head suspension for a connection between the head suspension and the main flexible circuit board as a functional part. For this connection, the similar problem is caused.
Further, such a problem is caused by solder jetting as well as the reflow soldering of the solder balls. The solder jetting is carried out by reflowing solder paste previously sprayed to the terminals to connect the terminals or spraying melted solder to the terminals to immediately connect the terminals. If the used amount of the solder decreases with the downsizing of the terminals, a problem similar to that of the small solder balls is caused.
Moreover, a recent head suspension may have piezoelectric elements as functional parts that are connected to a flexure in order to minutely position a magnetic head. In this case, conductive paste is used for a connection between terminals of the flexure and the piezoelectric elements. If the used amount of the conductive paste decreases with, for example, the downsizing of the head suspension, a connection failure is caused similar to the above.